netdev - [net-next 3/7] e1000e: fix timing for 82579 Gigabit Ethernet controller

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Date:   Thu, 20 Apr 2017 16:33:31 -0700
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Bernd Faust <berndfaust@...il.com>, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 3/7] e1000e: fix timing for 82579 Gigabit Ethernet controller

From: Bernd Faust <berndfaust@...il.com>

After an upgrade to Linux kernel v4.x the hardware timestamps of the
82579 Gigabit Ethernet Controller are different than expected.
The values that are being read are almost four times as big as before
the kernel upgrade.

The difference is that after the upgrade the driver sets the clock
frequency to 25MHz, where before the upgrade it was set to 96MHz. Intel
confirmed that the correct frequency for this network adapter is 96MHz.

Signed-off-by: Bernd Faust <berndfaust@...il.com>
Acked-by: Sasha Neftin <sasha.neftin@...el.com>
Acked-by: Jacob Keller <jacob.e.keller@...el.com>
Tested-by: Aaron Brown <aaron.f.brown@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index e9af89ad039c..667fc45ce906 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -3511,6 +3511,12 @@ s32 e1000e_get_base_timinca(struct e1000_adapter *adapter, u32 *timinca)
 
 	switch (hw->mac.type) {
 	case e1000_pch2lan:
+		/* Stable 96MHz frequency */
+		incperiod = INCPERIOD_96MHz;
+		incvalue = INCVALUE_96MHz;
+		shift = INCVALUE_SHIFT_96MHz;
+		adapter->cc.shift = shift + INCPERIOD_SHIFT_96MHz;
+		break;
 	case e1000_pch_lpt:
 		if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) {
 			/* Stable 96MHz frequency */
-- 
2.12.2